1. Field of the Invention
The field of the present invention relates to air intake apparatus for a vehicle, particularly a motorcycle or a motor-tricycle, in which a portion of the body frame is utilized as a passage for the intake air which is introduced into an engine mounted thereon.
2. Description of the Prior Art
One type of vehicle has heretofore been arranged such that a portion of the body frame is utilized as a passage for the intake air which is introduced into an engine mounted thereon. Such an earlier device prior art has been disclosed, for example, in the specification of Japanese Utility Model Publication No. 39758/78.
To increase the output performance of vehicles of the type described above, it is general practice to employ an engine having a large piston displacement. Employment of such an engine requires more intake air; consequently, it is necessary to increase the capacity of the air intake passage formed in the body frame correspondingly.
To increase the capacity of the air intake passage in the above-described prior art, it is necessary to form the main pipe used as the air intake passage with as large a diameter as possible. However, as the diameter of the main pipe is increased, the following problems arise:
(1) It becomes more difficult to weld the main pipe together with another constituent member of the body frame such as a head pipe. PA1 (2) Bending the main pipe limits the capacity of the air intake passage. PA1 (3) Increasing the diameter of the main pipe unfavorably increases the weight of the body frame.